The relationship between smoking and suicidal behavior, comorbidity, and course of illness in bipolar disorder

The rate of smoking in people with bipolar disorder is much greater than in the general population, but the implications of smoking for the course of bipolar disorder have not been well studied. The purpose of this retrospective study was to examine the relationship between smoking, severity of bipolar disorder, suicidal behavior, and psychiatric and substance use disorder comorbidity.

We evaluated 399 outpatients with bipolar disorder who were treated in a bipolar specialty clinic from December 1999 to October 2004. Diagnosis, mood state, course of illness, functioning, and psychiatric comorbidities were assessed using the Affective Disorders Evaluation and the Mini-International Neuropsychiatric Interview.

Of the 399 patients evaluated, 155 (38.8%) had a history of daily smoking. Having ever smoked was associated with earlier age at onset of first depressive or manic episode, lower Global Assessment of Functioning scores, higher Clinical Global Impressions-Bipolar Disorder scale scores, lifetime history of a suicide attempt (47% for smokers vs. 25% for those who had never smoked), and lifetime comorbid disorders: anxiety disorders, alcohol abuse and dependence, and substance abuse and dependence. In a logistic regression model including these factors, suicide attempts and substance dependence were significantly associated with smoking in patients with bipolar disorder.

Bipolar patients with lifetime smoking were more likely to have earlier age at onset of mood disorder, greater severity of symptoms, poorer functioning, history of a suicide attempt, and a lifetime history of comorbid anxiety and substance use disorders. Smoking may be independently associated with suicidal behavior in bipolar disorder.